This point of interest is supposed to prevent invasion on that system (unless it is Aelderi)

Yet a tyrannid fleet is invading it. Did I misunderstood the description or this is because it is a scripted invasion or bug ?

You need to level it to level 3.

@bosie Description says level I prevent assault on the -Obsidian Depths- system...the exact same system being assaulted on the screenshot

can confirm i have it level 3 and am still getting nid invasions

I had mine up to level 3 and I had invasions happening. Regardless, level 1 says that specific system is immune by default.

Yeah, it's not working; I have the thing at level 3 and I'm still getting invaded.

I believe the 'nid invasions are scripted (as part of the Tyranid invasion story arc) and as such are not affected by the planet upgrade. I had it at level 3 when they happened, but after fighting them off (currently on turn 125 of medium campaign) haven't had any other invasions in that sector aside from Eldar - so seems to be working on my end.

@yorilo the invasion on my screenshot appeared after I completed the Invasion part 1 scripted mission (3 reinforcement fleets arrived)

It’s scripted to be invaded by either one or two Tyranid fleets once you complete the Belis Corona mission no matter what.

'Nids don't follow the rules, they eat them!